Article
Multidisciplinary Sciences
Vladimir Fokin, Dmitry Minakov, Pavel Levashov
Summary: The dynamic electrical conductivity of dense Zr plasma near melting is calculated using ab initio molecular dynamics and the Kubo-Greenwood formula. The influence of computational parameters and inner shell electrons on the results is thoroughly investigated. The convergence of the computations and comparison with experimental data are demonstrated.
Article
Engineering, Electrical & Electronic
Taco Boland, Rik Naus, Peter Zwamborn
Summary: The paper discusses the challenges of measuring the phase response of large systems compared to magnitude response, and proposes using KK relations to relate magnitude and phase. It also presents a method to determine the locations of zeros in the right half of the complex plane for non-minimum phase systems, allowing for successful application of modified KK relations for phase response calculations.
IET SCIENCE MEASUREMENT & TECHNOLOGY
(2021)
Article
Chemistry, Multidisciplinary
Yea-Shine Lee, Sina Abedini Dereshgi, Shiqiang Hao, Matthew Cheng, Muhammad Arslan Shehzad, Christopher Wolverton, Koray Aydin, Roberto dos Reis, Vinayak P. Dravid
Summary: In this study, the spatially resolved dielectric functions of Si@MoS2 with nanoscale spatial resolution were extracted using valence electron energy loss spectroscopy (VEELS) and verified through simulations. The contribution of the Si/MoS2 interface was further explored using a cross-sectioned core-shell structure.
Article
Chemistry, Multidisciplinary
Chiara Trovatello, Florian Katsch, Qiuyang Li, Xiaoyang Zhu, Andreas Knorr, Giulio Cerullo, Stefano Dal Conte
Summary: In this study, transient optical response of single-layer WS2 was measured using ultrashort laser pulses, and the effects of many-body interactions and Coulomb correlations on excitonic resonances were analyzed. It was found that resonant photoexcitation caused a blue shift of the A exciton, while above resonance photoexcitation resulted in a reduction of the exciton oscillator strength dominating the transient response at the optical bandgap.
Article
Mathematics, Applied
Adam A. Sliwiak, Nisha Chandramoorthy, Qiqi Wang
Summary: This paper introduces a numerical procedure to assess the differentiability of statistics with respect to parameters in chaotic systems, based on the Lebesgue-integrability of a density gradient function, and develops a recursive formula for computing the density gradient, demonstrating its use in determining the differentiability of statistics.
COMMUNICATIONS IN NONLINEAR SCIENCE AND NUMERICAL SIMULATION
(2021)
Article
Chemistry, Physical
Tomasz P. Stefanski, Jacek Gulgowski, Kosmas L. Tsakmakidis
Summary: This paper comprehensively reviews several general methods and analytical tools for causality evaluation of photonic materials. The authors collect a set of various distributional theorems as the distributional version of the Titchmarsh theorem, allowing for evaluation of causality in complicated electromagnetic systems. They also correct existing material models using distribution theory to obtain their causal formulations. In addition to the Kramers-Kronig relations, four further methods are overviewed for assessing causality of given dispersion relations. These methodologies should be useful for scientists and engineers analyzing causality problems in electrodynamics and optics, particularly with regard to photonic materials when mathematical distributions are involved.
Article
Mathematics, Applied
Adam A. Sliwiak, Qiqi Wang
Summary: This paper proposes an algorithm for sensitivity analysis of chaotic systems with an arbitrary number of positive Lyapunov exponents. By combining perturbation space-splitting and measure-based parameterization, trajectory-following recursive relations and a memory-efficient Monte Carlo scheme are derived to compute the derivatives of the output statistics accurately.
SIAM JOURNAL ON SCIENTIFIC COMPUTING
(2022)
Article
Construction & Building Technology
Atanu Behera, Stephane Charmot, Ahmed Asif, J. Murali Krishnan
Summary: The study focuses on the repeated haversine compression test of emulsified cold-recycled asphalt mixture (ECRM) at different temperatures and frequencies, considering the influence of confinement pressure. The viscoelastic response of ECRM under various loading conditions is observed through Lissajous plots analysis. The dynamic modulus and phase angle are calculated using regression and FFT methods, with a model-based approach showing excellent predictive capabilities for the dynamic modulus of ECRM.
JOURNAL OF MATERIALS IN CIVIL ENGINEERING
(2021)
Article
Engineering, Mechanical
Adam A. Sliwiak, Qiqi Wang
Summary: This paper investigates the computation problem of parametric derivatives in the presence of chaos. Based on Ruelle's formalism, it proposes a method to simplify the linear response algorithm in higher-dimensional systems featuring statistical homogeneity. The study shows that the contribution of the SRB measure gradient can be negligible if the objective function is appropriately aligned with unstable manifolds. Several numerical examples support these conclusions and demonstrate the use and performance of the simplified linear response algorithm.
NONLINEAR DYNAMICS
(2023)
Article
Nanoscience & Nanotechnology
Fariba Ahmadi, Houshang Araghi
Summary: In this study, the electronic structure, dielectric, optical, and phonon properties of PbTiO3/CaTiO3/SrTiO3 ferroelectric superlattices were investigated using density functional theory. The superlattice was found to have a semiconducting phase with strong Ti-3d and O-2p state hybridization, along with stable optical and phonon properties.
JOURNAL OF NANOPHOTONICS
(2021)
Article
Mechanics
G. G. Sheng, Yan Han, Zihang Zhang, Lei Zhao
Summary: This study investigates the nonlinear free and forced vibrations of functionally graded cylindrical microshells conveying viscous fluid, considering size effects and viscous forces. The critical flow velocity and natural frequency are obtained numerically, and the effects of axial load, scale parameter, fluid flow velocity and viscosity on nonlinear dynamic response are studied. Comparisons with inviscid case and previous literature are also discussed.
COMPOSITE STRUCTURES
(2021)
Article
Engineering, Electrical & Electronic
Zsolt Szabo
Summary: By revisiting the derivation of the Kramers-Kronig relations based on system theory considerations, their general validity and connection to the causality of a linear system are demonstrated. The closed form Kramers-Kronig and subtractive Kramers-Kronig relations are introduced using shape-preserving third-order piecewise cubic interpolation, allowing accurate results to be obtained over a broad frequency range with only a small number of properly chosen data points. These developed formulas are applied to validate transfer functions, determine phase shifts, and extract refractive indices in various applications.
IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES
(2021)
Article
Optics
Gong Xiaoxue, Zhang Tiantian, Zhang Qihan, Zhang Tiening, Guo Lei
Summary: This study proposes the use of KK receiver to eliminate SSBI at the receiver side of the DD-OOFDM system, reducing BER and improving system transmission reliability. Secure transmission is achieved through chaotic encryption and OFDM modulation, ensuring data security and spectral efficiency improvement.
ACTA OPTICA SINICA
(2023)
Article
Physics, Condensed Matter
Kiryl Asheichyk, Matthias Fuchs, Matthias Krueger
Summary: In this study, we comprehensively investigate the linear response of interacting underdamped Brownian particles to simple shear flow through six different computational methods, revealing interesting effects due to interactions and finite particle mass. We compare the statistical efficiency of the different methods and discuss measures of breakdown of linear response theory for larger shear rates.
JOURNAL OF PHYSICS-CONDENSED MATTER
(2021)
Article
Engineering, Electrical & Electronic
Daniel Semrau, Eric Sillekens, Robert Killey, Polina Bayvel
Summary: The research reveals that the direct implications of the real part of the Raman spectrum on nonlinear distortions in optical fibers have not been extensively explored. A theory is proposed in this work to quantitatively assess the impact of the real Raman spectrum on nonlinear interference power (NLI), offering a new perspective on understanding and modeling nonlinear signal distortion.
JOURNAL OF LIGHTWAVE TECHNOLOGY
(2021)
Article
Mathematics, Applied
Davide Faranda, Tommaso Alberti, Maxence Arutkin, Valerio Lembo, Valerio Lucarini
Summary: The suspension of vaccination campaigns can lead to more excess deaths, even when taking into account the potential side effects of the vaccine.
Article
Mathematics, Applied
Manuel Santos Gutierrez, Valerio Lucarini, Mickael D. Chekroun, Michael Ghil
Summary: This study establishes a strong connection between data-driven and theoretical approaches to achieving efficient and accurate parameterizations for model reduction. Through perturbation expansions, a general stochastic parameterization of weakly coupled dynamical systems is derived, and it is shown that truncation of expansions is not necessary when coupling is additive. Additionally, the study simplifies unwieldy integrodifferential equations into a multilevel Markovian model and establishes an intuitive connection with a generalized Langevin equation. This research supports the physical basis and robustness of the empirical model reduction (EMR) methodology while highlighting the practical relevance of the perturbative expansion used for deriving the parameterizations.
Article
Astronomy & Astrophysics
Melanie Kobras, Maarten H. P. Ambaum, Valerio Lucarini
Summary: The study highlights the nonlinear mechanism of eddy saturation in geophysical flows and presents a simplified baroclinic model with stable solutions, showing the increasing attraction of eddy solution with the increment of baroclinic forcing.
GEOPHYSICAL AND ASTROPHYSICAL FLUID DYNAMICS
(2022)
Article
Mathematics, Applied
Chiara Cecilia Maiocchi, Valerio Lucarini, Andrey Gritsun
Summary: This article investigates the approximation of chaotic trajectories in the Lorenz 1963 model using unstable periodic orbits (UPOs). The study finds that longer period UPOs provide a better local approximation to the trajectory. Additionally, by constructing a Markov chain and analyzing the scattering of the orbit between different UPO neighborhoods, a different interpretation of the mixing processes in the system is provided using the concept of quasi-invariant sets.
Article
Physics, Multidisciplinary
Manuel Santos Gutierrez, Valerio Lucarini
Summary: The perturbation theory of operator semigroups is used to derive response formulas for various combinations of acting forcings and reference background dynamics. The linear response gives the correction to expectation values due to extra deterministic forcings acting on either stochastic or chaotic dynamical systems.
JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL
(2022)
Article
Environmental Sciences
Valerio Lucarini, Vera Melinda Galfi, Jacopo Riboldi, Gabriele Messori
Summary: Understanding the statistical properties of extreme weather events and their underlying physical processes is crucial for evaluating climate variability, climate change, and associated hazards. Recent studies have shown that large deviation theory (LDT) is useful for investigating persistent extreme events and estimating long return periods. In this study, we utilize LDT and a state-of-the-art Earth system model to analyze the 2021 Western North America summer heatwave. We find that the occurrence of the heatwave can be attributed to climate variability, but its probability is greatly amplified by ongoing climate change. We also examine the spatial coherence and the role of the Rocky Mountains in influencing extreme events in the Western Pacific region of North America.
ENVIRONMENTAL RESEARCH LETTERS
(2023)
Article
Mathematics, Applied
T. Alberti, D. Faranda, V. Lucarini, R. V. Donner, B. Dubrulle, F. Daviaud
Summary: Natural systems exhibit emergent phenomena at different scales, with chaotic behavior at large scales and randomness at small scales. The properties of the underlying attractor, which hosts the system trajectories, are usually studied quantitatively to understand these features. However, the multi-scale nature of natural systems makes it difficult to obtain a clear picture of the attracting set. In this study, we use an adaptive decomposition method and extreme value theory to analyze the scale-dependent dimension of the attractor, showing that it can discriminate between different types of noise.
Article
Mathematics, Applied
P. Cannarsa, V. Lucarini, P. Martinez, C. Urbani, J. Vancostenoble
Summary: We study a two-layer energy balance model that considers the vertical exchanges between the surface layer and the atmosphere. The coupling between the surface temperature and the atmospheric temperature is influenced by the emission of infrared radiation and non-radiative vertical energy exchanges. The absorptivity of the atmosphere, denoted as epsilon a, plays a crucial role and is affected by greenhouse gases. The research proves the existence of solutions when epsilon a is within the range of (0, 2) and indicates finite time blow up if epsilon a > 2. The long term dynamics are explained for epsilon a ∈ (0, 2), showing convergence to equilibrium points. Additionally, the dependence of equilibrium points on the involved parameters is studied, highlighting the monotonic increase of surface temperature with respect to epsilon a, which is the mathematical manifestation of the greenhouse effect.
Article
Mathematics, Applied
Melanie Kobras, Valerio Lucarini, Maarten H. P. Ambaum
Summary: In this study, a minimal dynamical system derived from the classical Phillips two-level model is introduced to investigate the interaction between eddies and mean flow. The study finds that the horizontal shape of the eddies can lead to three distinct dynamical regimes, and these regimes undergo transitions depending on the intensity of external baroclinic forcing. Additionally, the study provides insights into the continuous or discontinuous transitions of atmospheric properties between different regimes.
PHYSICA D-NONLINEAR PHENOMENA
(2024)
Article
Multidisciplinary Sciences
Denis-Didier Rousseau, Witold Bagniewski, Valerio Lucarini
Summary: The Earth's climate has undergone numerous critical transitions throughout its history, accompanied by significant changes in the biosphere. By studying proxy records across different timescales, the aim is to identify, date, characterize, and rank past critical transitions, providing a more comprehensive understanding of climatic history.
SCIENTIFIC REPORTS
(2023)
Article
Physics, Multidisciplinary
Niccolo Zagli, Grigorios A. Pavliotis, Valerio Lucarini, Alexander Alecio
Summary: This article presents a model describing a group of identical interacting agents subject to multiplicative noise. These systems exhibit continuous and discontinuous phase transitions in a generally nonequilibrium setting. The authors provide a systematic dimension reduction methodology for constructing low-dimensional, reduced-order dynamics based on the cumulants of the probability distribution of the infinite system. They show that this approach accurately represents the system's stationary phase diagram and captures its response to external perturbations.
PHYSICAL REVIEW RESEARCH
(2023)
Article
Mathematics, Applied
Chiara Cecilia Maiocchi, Valerio Lucarini, Andrey Gritsun, Yuzuru Sato
Summary: The predictability of weather and climate is influenced by the state-dependent nature of atmospheric systems. The presence of special atmospheric states, such as blockings, is associated with anomalous instability. Chaotic systems, like the attractor of the Lorenz '96 model, exhibit heterogeneity in their dynamical properties, including the number of unstable dimensions. The variability of unstable dimensions is linked to the presence of finite-time Lyapunov exponents that fluctuate around zero. These findings have implications for understanding the structural stability and behavior modeling of high-dimensional chaotic systems.
PHYSICA D-NONLINEAR PHENOMENA
(2024)
Article
Geosciences, Multidisciplinary
Lucy G. Recchia, Valerio Lucarini
Summary: The South Asian and East Asian summer monsoons are globally significant meteorological features. Future changes in concentrations of aerosols and greenhouse gases may impact monsoonal precipitation, with the most significant decrease observed in eastern China and least impact on precipitation in southern India.
EARTH SYSTEM DYNAMICS
(2023)
Article
Physics, Fluids & Plasmas
G. Margazoglou, L. Biferale, M. Cencini, G. Gallavotti, V Lucarini
Summary: This study investigates a reversible version of three-dimensional Navier-Stokes equations and addresses two important questions through simulations: the conditions for statistical equivalence between non-equilibrium ensembles, and the empirical distribution of fluctuating viscosity with respect to Reynolds number and the number of modes used in the discretization of the evolution equation.
Article
Geosciences, Multidisciplinary
Valerio Lucarini, Larissa Serdukova, Georgios Margazoglou
Summary: This study investigates the impact of applying stochastic forcing in the form of fluctuating solar irradiance to the Ghil-Sellers energy balance climate model. By conducting numerical simulations, the researchers explore the noise-induced transitions between warm and snowball climate states and compare the statistics of transition times under Gaussian and alpha-stable Levy noise laws. The study highlights significant differences in transition paths between Gaussian and Levy noise cases, especially in terms of the residence time in metastable states and the most probable transition paths.
NONLINEAR PROCESSES IN GEOPHYSICS
(2022)